Method of precooling cargoes of vegetable products



Dec. 7, ,1943. A Y PREBL' 2,336,125

METHOD OF PRECOOLING VCARGOES OF VEGETABLE PRODUCTS Filed March 24 1941 wf M l aqtomzyf Patented Dec. 7, 1943 UNITED STATES PATENT OFFICE METHOD F PRECOOLING CARGOES OF VEGETABLE PRODUCTS Andrew Y. Preble, El Centro, Calif. Application March 24, 1941, Serial No. 384,864

3 Claims.

The present invention is particularly applicable for cooling or precooling vegetable products packed into cargo space on a freight car, or other carrier; and one of the objects of the invention is to provide a simple method for reducing the time necessary to be consumed in reducing the temperature in' the cargol space, and for more effectively accomplishing the reduction of temperature of the vegetable products. While the invention is applicable for precooling any kind of vegetable product, it is particularly useful when applied for cooling cargoes of lettuce, cabbage, or other fresh vegetables that must be maintained in a fresh condition during transit.

Further objects of the invention will appear hereinafter.

The invention consists in the novel steps and combination of steps to be described hereinafter, all of which contribute to produce an'efcient method of precooling cargoes of vegetable products.

A preferred embodiment of the invention is described in the following specification, while the broad scope of the invention is pointed out in the appended claims.

In the drawing:

Fig. 1 is a longitudinal section through a freight car, in which the method is practiced.

Fig. 2 is a cross-section upon an enlarged scale through the car body opposite the door, taken on the line 2-2 of Fig. 3, certain parts being broken away or shown in elevation. trates the precooling unit alongside of the car and connected to the same for circulating cooled gas4 or air through the interior of the carf'and also illustrates the simple apparatus which I employ in practicing my method.

Fig. 3 is a vertical section, and shows the mid dle portion of the car body and o'or grating upon an enlarged scale, to further illustrate the circulation of the cooling gas or air into and out of the car.

Fig. 4 is a. face view 'of the false door which is employed in circulating the cooling gas or air This View illusthrough the car. This view is of a more or less diagrammatic nature, and shows the circulation inlet and outlet in cross-section. This view also illustrates the hose and pipe connection for bringing water into the circulation duct. This view may be considered a vertical section on the line 4 4 of Fig. 2.

In practicing this method, I circulate a cool gas through the cargo space, and this gas or air Vcarries a high percentage of moisture or water in suspension. This water deposits on the interior of the walls of the cargo space, and if the cargo is composed of vegetable products, the

vmoisture also deposits on their superficial sur-` face. In practicing the process, I prefer to circulate the air continuously through the interior of the cargo space and through a cooling unit or heat exchanger in which the air or gas employed, is cooled. As the air circulates, I supply water to it in an atomized state, so that the water is carried in suspension. Vegetable products are usually shipped in open crates, that is, they are open on their ends so that the air, circulating through the crate, and highly charged with moisture, has access directly to the vegetable products, and hence a considerable deposit of moisture on the product occurs. This moisture is, of course, in a cooled state at the time of its deposit, but may even have its temperature reduced after being deposited.

'I'he car in which I may practice this method,

The ends of the car are provided with ice bunkers 4 carrying broken ice 5. The partition wall 6 between the interior of the bunkers 4 and the cargo space-are provided withY circulation openings l which may be closed when desired, by means of a shutter or door 8. The crates 3 are preferably of open construction, that is to say, they are formed of slats as indicated by the crate 3a indicated in full lines in Fig. 1.

In order to precool the cargo space, I place a false door 9 in the doorway Ill of the car, which doorway is located at about the middle of the car as indicated. This falsel door is preferably formed of two sections 9a and- 9b, one of which closes the left side of the doorway; the other the right side. The adjacent edges of these sections may be formed with deep notches Il and Ha, which come together to form the inlet I2 and outlet I3 for the circulating gas or air.

As fully described in my prior application, Patent No. 2,274,162, granted February 24, 1942, the squeeze or space I4 opposite the doorway, is provided with side walls i5 and a cover wall i6, that cooperate to form a deep lateral duct il in this space, and the lateral space, or duct i8 above the cover wall it.

When the car is being cooled, it is run onto a siding opposite a cooling unit i9, provided with cooling coils and means for extracting heat from the air being circulated through the unit, including a fan 2li indicated in dotted lines in Fig. 2. The fan delivers the cooled gas or air through a flexible conduit 2i that connects to the lower inlet opening l2 in the false door, and the outlet opening i3 from the false door is connected through a similar iexible conduit 22 to the inlet side of the cooling unit i9. The car has a false ybottom in the form of a grating 23, or any other suitable construction to facilitate free'movement of the cooled gas ory air through the cargo. In the present instance, the grating is laid on longitudinal stringers 24 that have the effect of forming a plurality of air ducts 25 extending 1ongitudinally under the grating so that as the air moves across the car, it passes down through the gra-ting and longitudinally toward the ends of the car in the ducts 25. As it passes along the ducts, of course, it passes up through the grating and bottom, and into the lattice-form crates that carry the vegetable products or fruit. As the air passes in through the inlet conduit 2i, moisture is added to it in considerable quantities, and this is preferably accomplished by providing a spray device 25 that may have two or more atomizer heads 21 through which the water is admitted in a fine spray. These nozzles preferably throw the spray against the air stream, that is to say, in a direction to oppose the stream of air passing into the car. This spray device 26 is preferably carried on an inlet pipe 28 that is rigidly secured to the inner side of one of the door sections, for example, the door section 9a. In this way the spray device will be located in the doorway. This arrangement makes it unnecessary to carry the inlet pipe 28 through the wall of the conduit' 2|. The water may be supplied from a service line 29 that may come out of the ground, and carry a valve 30 to which a hose V3i is connected, to carry the water to an inlet elbow 32 located on the outer side of the door section 9a, and connected with the inlet pipe 28.

The practice of this method results in a considerable reduction in the time usually consumed in precooling a loa-d in the interiorI space in a v freight car. The reasons for this appear to be that the water that is atomized into the circulating air stream, which is being circulated through a closed circ'uit causes the air stream to carry particles of water in mechanical suspension, and as the air circulates in the space immediately surrounding the articles such as constitute the vegetable product in the car, moisture from the air is deposited on the vegetables, and at the same time, the presence of the moisture in the composite circulating stream causes the latter to have a specic heat much greater than that of the air alone; that is to say, it raises the eiectiveness of the air in extracting heat from the articles in the path of the air stream. The presence of the 'deposited moisture on the vegetables, adds greatly to the efficiency of this methodbecause this deposited moisture assists in extracting the heat from the vegetables, and acts as a good conductor in transferring this heat to the highly saturated lair stream as it ows through the car and in contact with the vegetables. The continued atomizing of the water into the air current maintains its high degree of saturation. Therefore, I believe that the greatest eiiiciency of this method is derived from the continuing circulation of the air stream after the moisture has been deposited on ,the surface of the vegetables, because in that stage of the operation I am utilizing the deposited moisture to conduct the heat from the articles to the air stream. And while this is occurring, I believe there is practically no evaporation of the mois ture from the surface of the vegetables, because the air stream is already carrying such a quantity of moisture that it would be substantially impossible to have it take up any more moisture, the degree of humidity being in the neighborhood of 90 to 93%.,`

It is optional to precool the cargo space 2 before or after the bunkers ll have been supplied with ice, ready for the departure of the loaded car. If iced, and the cooling air or gas is being circulated through the cargo space, the shutters 8 for the circulating openings l, are maintained closed. This enables the cargo space to be thoroughly cooled without causing any melting of the ice. After the precooling is completed, these shutters 8 should 'be placed in an open position so as to permit free circulation of air through the bunker space and through the cargo.

The air or gas is, of course, withdrawn from the space i8 through the withdrawal duct 22, by the action of the fan.

If desired, the side walls l5 may beprovided with depressed openings iSd through which the cool air may pass, to insure thorough distribution of the coolingv air currents through the cargo.

In practicing this process, it is immaterial whether the water is cold or not. If the water is taken from an underground pipe in warm weather, its temperature may run from to 100 F. In practicing this method, I have found it possible to develop a humidity within the product load compartment, from to 93 per cent. This high percentage of humidity is very desirable when shipping certain products.

The depositing of this considerable amount of moisture "on the inner faces of the walls of the cargo space, and on the surfaces of the crates and on the product itself, results in making the interior of the car quite cold and clamp. After the car commences its trip toward its destination, of course, the interior of the car will tend to become drier; but as a result of the method, there will always be a considerable area on which water is resting, and from which it is evaporated.

Ihis evaporation absorbs a considerable amountl of heat, so that the method is very effective in maintaining a low temperature for the cargo space during transit, and for reducing the quantity of ice that is necessary for carrying the cargo through to its destination, and with the cargo space maintained 'at a desired low tem? perature.

My experience in using this method in practice, seems to indicate that the deposit of moisture is increased if the water is warmer than the circulating air. Evidently the high degree of saturation with relatively warm water vapor and Water in suspension,vraises the dew point, which of course would increase the moisture deposit.

be resorted to without departing from the spirit of the invention.

What I claim is:

l. A method of cooling a load of fruit or vvegetable products arranged in a cargo shipping space, comprising: moving an air stream continuously through a closed circuit having a horizontally disposed component in said cargo shipping space, continuously atomizing water and projecting the Water particles counter current into said moving air stream as it enters said shipping space, continuously causing the stream of air and water to travel 'through said load and deposit Water upon said products, and cooling said stream in a portion of said closed circuit outside of said cargo shipping space.

2. A method of cooling a load of fruit or ve'ge-vtable products arranged in a cargo shipping tinuously through a closed circuit having a hori- Zontally disposed component in Said cargo shipping space, continuously atomizing water and projecting the Water particles counter current into said moving air stream as it enters said space, comprising: moving an `air stream' conshipping space, continuously causing the stream of air and water to travel through said load thereby increasing the humidity of said air to approximately 90% and effecting the deposit of water upon said products; and cooling said stream in a portion of said closed circuit outside of said cargo shipping space.

3. A method of cooling articles in an enclosed space, which consists in circulating a stream of cool air through a closed circuit including said space; atomizing water into the said air stream to develop a high degree of humidity in the air stream and cause the moisture to be carried in suspension in the air stream, thereby in eiect raising the specific heat of the air stream, and also causing the circulating air stream to deposit moisture on the articles; and continuing the circulation of the air stream and simultaneously replacing the moisture deposited on the said articles by additional moisture atomized into said stream so as to utilize the deposited moisture Ato conduct the heat from the articles and transfer 

